Rotary pump or expansion engine



Jan. 8, 1963 K. B. MOSSIN 3,072,315

ROTARY PUMP OR EXPANSION ENGINE Filed July 8, 1958 3 Sheets-Sheet 1 Jan.8, 1963 K. B. MOSSIN 3,

ROTARY PUMP OR EXPANSION ENGINE Filed July 8, 1958 3 Sheets-Sheet 2/IIIIIIIIIIIIIIIIIII% Jan. 8, 1963 K. B. MOSSIN 3,072,316

ROTARY PUMP 0R EXPANSION ENGINE Filed July 8, 1958 3 Sheets-Sheet 3INVENTOR KQ'Z Barge Moss/A1 ATTORNEYS rates The present inventionrelates to a rotary pump or expansion engine comprising two rotorsrotating in opposite directions in a case which in cross section has theshape of two mutually overlapping circles, one of said rotors having onetooth and being convex in cross section, at any rate as regards thegreater part of it, and rotating on an axis eccentric in relation to thegeometrical centre of the cross section, while the other rotor has twoteeth and rotates on an axis, which is centric in relation to thegeometrical centre of the rotor cross section, at a rate of revolutionequal to halt the number of revolutions of the former rotor.

Such rotary pump or expansion engine is for example known from thespecification of British Patent No. 663,- 928 which in detail describesan embodiment with a singletooth rotor and a triple-tooth rotor, butalso discloses that the triple-tooth rotor may be substituted by adoubletooth rotor which in cross section approximately has the shape ofa rectangle, the length of which is of the same size as the diameter ofthe cylindrical working space of this rotor. The two short sides of therotor cross section are not rectilinear, however, but are formed bycircular arcs with a diameter corresponding to the width of the rotorcross section. During the operation, the two co-operating rotors are atany time in contact with each other along at least one line, and each ofthe teeth on the multi-tooth rotor furthermore forms a line sealingalong the wall of the working space of this rotor. The single-toothrotor may in a similar way be in line contact with the wall of theworking space of this rotor, but may also be so formed as to touch thesaid wall over a sector of egg. about 30.

The construction referred to in the said patent specification is statedto have a smaller clearance space than the rotary pumps or expansionengines known in advance and thus a better efliciency than the latter.

The present invention is based on the cognition that a furtherconsiderable reduction of the clearance space may be obtained togetherwith other advantages when the double-tooth rotor in cross section hassubstantially the form of a double-bitted battle-axe, the crown of eachtooth being formed by a circular-arc shaped part of the periphery of therotor with its centre in the centre of the cross section thereof andwith a comparatively considerable extent in the peripheral direction,while the width of the cross section of the tooth at any rate in theouter portion ofeach tooth decreases towards the centre.

An advantage of this construction (in addition to the reduction of theclearance space) consists in that the sealing zone between each of theteeth of the double-tooth rotor and the wall in the associated workingcompartment extends over a considerable sector or arc, which gives abetter sealing between the tooth and the wall than in the case of linearcontact for the reason that the tooth is to slide along the wall andtherefore can have no firm abutment on or firm contact with the latter.The wide contact face between the crown of the tooth and the wall of theworking compartment furthermore opens up the prospect of designingshallow sealing grooves in at least one of the co-operatiug faces forthe further increase in the resistance against the passage of theworking fluid from the high-pressure side of the tooth to itslow-pressure side.

" atent O M Patented Jan. 8, 1963 According to the invention, theperiphery of the singletooth rotor preferably comprises a first sectorconcentric with the axis of rotation of this rotor for cooperation withthe circular-arc-shaped crown of each of the teeth of the double-toothrotor, and an oppositely located second sector which is likewiseconcentric with the axis of rotation and forms the crown of the tooth ofthis rotor. During the operation, said first sector will roll or slideon the tooth crowns of the double-tooth rotor, so that at this point aconsiderable sealing can be obtained, and at the same time the secondsector of the single-tooth rotor will over a considerable anglecooperate with the wall of the working compartment of this rotor, sothat at this point there will also be a great resistance against passagefrom the high-pressure side to the low-pressure side.

The periphery between the tooth crowns of the doubletooth rotor isaccording to the invention advantageously formed by at any ratesubstantially concave faces with substantially the same curvature as thecrown of the tooth of the single-tooth rotor. An advantage of thisarrangement is that the pressure of the working fluid on thedouble-tooth rotor may be distributed tolerably evenly in the positionof the rotors corresponding to the highest pressure of the workingfluid, and hereby a turning moment on the double-tooth rotor caused bythe working fluid can be avoided.

In a preferred embodiment of the rotary pump or the expansion engineaccording to the invention the crowns of the teeth of the double-toothrotor continue into the flanks of the teeth through short transitionroundings which form line sealing against the single-tooth rotor overthe greater part of the periphery of the latter. During the operation ofthe pump or engine the line of contact between the two rotors willlinger at the said transition roundings and so to speak skip thesubstantially concave faces of the double-tooth rotor.

In an expedient embodiment of the rotary pump or expansion engine it isof the type (known for example from the British patent specificationmentioned above) where inlet and outlet channels for the working fluidterminate in the working space through slot-shaped openings in thevicinity of the point of intersection of the circles determining thecross section of the working space, at any rate the one of the saidchannels, in which the Working fluid is under the highest pressure,terminating in the working compartment for the double-tooth rotor andcontaining a valve which is located close to the said workingcompartment and is operated in time with the rotor. In this case theopening of the latter channel is, according to the present invention,advantageously in permanent communication with the working compartmentof the single-tooth rotor at a point near this opening. The permanentcommunication may for example be provided by cutting away parts of thewall of the working compartment of the double-tooth rotor between theopening of the channel and the Working compartment of the single-toothrotor. This permanent communication will certainly, whether it beprovided by the said cutting away or in some other way, entail anincrease of the clearance space in the pump or expansion engine, but,firstly, this increase need only be rather insignificant and, secondly,the permanent communication possesses the special advantage that thepressure fluid from the working compartment of the singletooth rotor mayflow evenly into the Working compartment of the double-tooth rotor sothat no passage losses will occur.

The invention will now be more fully described with reference to thedrawing, in which:

FIG. 1 illustrates a diagrammatical cross section through an embodimentof the machine with the two rotors and the associated rotary valve in afirst position,

FIGS. 2 and 3 are similar views of the same elements in two otherpositons during operation,

KG. 4 is a fragmental sectional view of a slightly modified embodimentof the invention, and FIG. 5 is an almost similar fragmental view of afur ther embodiment.

In the drawing, 1 designates the case of the apparatus which comprisestwo partly overlapping cylindrical working compartments 2 and 3. Aninlet or admission channel 4 terminates 'in the interior of the casethrough a slot-shaped opening 5 which in the embodiment shown is incommunication with both working compartments 2 and 3, but may also be incommunication with only one of the said two working compartments.

Opposite the inlet opening 5 there is in the wall of the workingcompartment 3 formed an outlet or discharge opening 6, the communicationof which with an outlet channel 7 is controlled by a rotary valve 8which is suitably accommodated in the outlet channel 7 and thecircular-arc-shaped sealing face of which co-operates with comparativelysmall sealing faces above and below the slot-shaped outlet opening 6,respectively.

In the working compartment 2 there is on a centrally 'journalled shaft lt) mounted a rotor 9, the cross section periphery of which comprises afirst sector a, which is concentric with the axis of rotation of therotor, i.e. the axis of the shaft it), and has a radius which isconsiderably smaller than half the diameter of the working compartment2, e.g. about one half of half the diameter of the latter, and a secondsector 12 which is concentric with the same axis and the radius of whichis equal to half the diameter of the working compartment 2. The twosectors a and b are interconnected through curved portions 11.

Centrallyin the working compartment 3 a shaft 1?; is journalled whichcarries a double-tooth rotor 13 which in cross section is shaped like adouble-bitted battle-axe, the cross section being bounded by twocircular arcs 14, which are concentric with the axis of the shaft 12,and two concave arcs 15 connecting the said arcs 14. These concave arcs15 may be substantially circular-arc-shaped, in which case their radiusof curvature is of the same size as or slightly smaller than the radiusof the sector b of the single-tooth rotor 9. The tooth crowns 14 of thedouble-tooth rotor 13 therefore have a considerable extent in thecircumferential direction which, as explained in the foregoing, makespossible a particularly effective sealing between these tooth crowns andthe wall of the working compartment 3 and, as also mentioned before,this sealing may be further improved by means of shallow grooves orcorresponding irregularities on at least one of the cooperating faces.Such grooves extending in the axial direction of the rotor 13 have beenindicated in FIG. 4.

Therotor 13 has in the embodiments shown short transition roundings 16between each of the tooth crowns 1'4 and the tooth flanks 15.

Between the outlet opening 6 and the working compartment 2 a permanentlyopen passage 17 is provided for the purpose explained in the foregoing.In the illus trated embodiments, this passage is formed by one or morerecesses extending through the portion or" the casing 1 separating theopening 6 from the compartment 2.

When the apparatus shown is to operate as a rotary pump, the rotors 9and 13 and the rotary valve are caused to rotate in the directionsindicated by the arrows and in such a way that the rate of revolutionfor the rotor 13 is half the rate of revolution for the rotor 9, therate of revolution of which is equal to the rate of revolution for therotary valve 8.

In the position in FIG. 1, the sector b of the singletooth rotor hasjust cut off the communication from theinlet channel 4- to thecompression chamber in the cylinder or compartment 2, and the right-handlower transition rounding of the double-tooth rotor 13 is in 41. sealingcontact with the right-hand curved portion 11 of the single-tooth rotorh. At the same time the opposite tooth crown on the [rotor 13 has cutof? the communication from the inlet channel 4 to the chamber above therotor This chamber is, however, via the outlet opening a, which isobstructed by the rotary valve 8, and the recess 17 in permanentcommunication with the compression chamber in the cylinder orcompartment 2, so that during the rotary motion of the rotors a uniformrise in pressure will occur in the intercommunicating chambers. If therecess 17 were not provided, the right-hand tooth of the (rotor 13 wouldform a separation between the two chambers during the first part of thecompression stroke, and the passage of the working fluid from thecompartment 2 to the compartment 3 would not commence until a pressureof a certain value had been produced in the compartment 2, and thereforethe sudden opening for the passage would be accompanied by a certainthrottling loss.

FIG. 2 shows the position of the different parts after the single-toothrotor 9 and the rotary valve 8 have turned about 180 from the positionin FIG. 1, while at the same time the double-tooth rotor 13 has turnedslightly less than In the position in FIG. 2 the rotary valve has openedthe outlet opening 6, and the working fluid is being forced out into theoutlet channel 7, the lower tooth crown 14 on the double-tooth rotormeanwhile being in sealing contact with the circular sector a of thesingle-tooth rotor 9. The opening point for the rotary valve 8 may beadapted to the pressure which it be desired to produce.

In FIG. 3 the different parts approach their positions at thetermination of the compression stroke. The circular section b of thesingle-tooth rotor 9 still seals against tie wall of the workingcompartment 2, and the lefthand curved portion 11 of this rotor is inline contact with the left-hand lower corner rounding of the doubletooth[rotor 13. The rotary valve 8 has partly obstructed the outlet opening6, but pressure fluid may still how out through this opening. From theposition in FIG. 3 the parts turn on, and the left-hand end of thecircular-arc-shaped sector b reaches the lower, left-hand cornerrounding lid of the double-tooth rotor 13, so that the space between thetwo rotors, ie. the clearance space of the machine, has reached itsminimum. At this point, the rotary'valve 3 completely obstructs theoutlet opening 6, and the whole of the concave, downwards-facing side orflank 15 of the double-tooth rotor 13 will be loaded with the pressureofthe working medium so that the latter exerts no unbalanced stress onthis rotor. During a very short further turning of the parts the line ofcontact between the two rotors 9 and 113 skips to the right-hand lowercorner rounding 16 of the rotor 13, which rounding will during thefurther turning slide on the right-hand curved portion 11 of thesingle-tooth rotor 9. The parts have now arrived into a positioncorresponding to that shown in FIG. 1.

It will be obvious that the apparatus illustrated in the drawing mayalso work as an expansion engine, this only necessitating that therotary valve 8 is given a rotary motion in the opposite direction to thearrow shown and that pressure fluid is supplied to the channel 7. Thetwo rotors 9 and 13 will then by the pressure medium be given a rotarymotion in the direction opposite to the arrows shown.

The turning valve 8 in the outlet channel 7 shown in FIGS. 1-3 oifersfavorable discharge possibilities, but also valves of other types may beused. Thus, in FIG. 4 a spring-loaded non-return valve 18 has been shownwhich is hinged as at 19 to a portion of the casing 1 and is permanentlyurged towards its closed position by means of a compression spring 20inserted between an appropriate part of a casing 1 and an arm 22 rigidlyconnected with the valve plate 18.

In FIG. 5' a transversely displaceable gate valve 22 has been shown. Byan appropriate mechanism (not shown) of conventional type, this gatevalve or slide valve may be moved between a closing position and an openposition indicated by broken lines in FIG. 5.

FIG. 4 also indicates that provisions may be made for cooling themachine during its operation, particularly when the machine is a highpressure rotary pump. Thus, reference numerals 23 and 24 in PEG. 4designate cooling fluid passages provided in the casing 1 of themachine.

Finally should be mentioned that due to the spcciai cross sectionalshape of the double-tooth rotor with comparatively deep cuts between theteeth the singletooth rotor may have an especially high ratio betweenits largest radius (sector 11) and its smallest radius (sector a), whichresults in a correspondingly large cross sectional area for thecompression chamber or the expansion chamber and consequently a highoutput per unit of length of the rotors.

I claim:

1. A rotary pump or expansion engine, having a casing enclosing aworking space comprising two intersecting compartments of circularcross-sectional shape, a first rotor journalled for rotation Within oneof said compartments about the axis thereof and having a peripheralsurface of cylindrical formation, the cross section of which is composedof a first sector concentric with said axis and of a radius considerablysmaller than the radius of the particular compartment, a second sectorconcentric with said axis and of substantially the same radius as saidcompartment, and two convex further smoothly curved sectionsinterconnecting the respective ends of said first and second sectors,said further sections having end portions extending tangential torespective ends of said first and second sectors, a second rotorjournalled for rotation within the other one of said compartments aboutthe axis thereof and having a peripheral surface of cylindricalformation, the cross section of which is that of a double bittedbattle-axe and composed of a first pair of opposite sectors concentricwith the axis of said other compartment and of substantially the sameradius as this compartment, and a second pair of opposite sectors of agenerally concave formation interconnecting the respective ends of thesectors of said first pair of opposite sectors, each sector of saidsecond pair of opposed sectors having a generally flat central portionand arcuate end portions, the spacing of said axes being equal to thecombined radii of said first rotor first sector and said second rotorfirst sector, a driving connection between said two rotors causing saidsecond rotor to revolve in operation in the opposite direction from thatof said first rotor and with a rotational speed equal to one half of therotational speed of said first rotor, the shapes of said second sectorand said further sections of the first rotor and said second pair ofopposite sectors of the second rotor being interrelated in such a mannerthat during operation the rotors contact each other at least along asingle line at all times, inlet and outlet ducts in said casing locatedone on each side of the second rotor and communicating with said workingspace and sealed from each other by the rotors, and a control valvedisposed in that one of said ducts in which the highest working pressureprevails during operation.

2. A rotary machine as claimed in claim 1, wherein each central portionof each sector of said second pair of sectors of said second rotor hassubstantially the same curvature as said second sector of said firstrotor.

3. A rotary machine as claimed in claim 1, wherein each of the sectorsof said first pair of o osite sectors of said second rotor continuesinto the adjacent ends of said second pair of sectors through shorttransition roundings which form line contact with said further sectorsof said first rotor during operation.

4. A rotary machine as claimed in claim 1, wherein one of the inlet andoutlet ducts in which the highest working pressure prevails duringoperation communicates with said other compartment of the working spacethrough a slot-shaped opening in the vicinity of one of the points ofintersection of said compartments, a rotary valve controlling saidopening and being located in close proximity to said other compartmentand operated in properly timed relation with said rotors, and saidopening below said valve communicating with the compartment within whichsaid first rotor operates, through at least one permanently open passageterminating in the latter compartment in the vicinity of said point ofintersection.

5. A rotary machine as claimed in claim 1, wherein the peripheral facesof said second rotor, corresponding with said first pair of oppositesectors, are roughened.

References Cited in the file of this patent UNITED STATES PATENTS508,574 Lambing Nov. 14, 1893 595,227 Wattles Dec. 7, 1897 1,698,802Montelius Jan. 15, 1929 1,821,523 Montelius Sept. 1, 1931 2,198,786Montelius Apr. 30, 1940 2,698,130 Mossin Dec. 28, 1954 2,920,610 BreelleJan. 12, 1960 FOREIGN PATENTS 20,174 Great Britain of 1909 663,928 GreatBritain Dec. 27, 1951 604,302 France Jan. 25, 1926 323,492 Italy Dec.24, 1934 721,481 Germany Feb. 19, 1943

1. A ROTARY PUMP OR EXPANSION ENGINE, HAVING A CASING ENCLOSING AWORKING SPACE COMPRISING TWO INTERSECTING COMPARTMENTS OF CIRCULARCROSS-SECTIONAL SHAPE, A FIRST ROTOR JOURNALLED FOR ROTATION WITHIN ONEOF SAID COMPARTMENTS ABOUT THE AXIS THEREOF AND HAVING A PERIPHERALSURFACE OF CYLINDRICAL FORMATION, THE CROSS SECTION OF WHICH IS COMPOSEDOF A FIRST SECTOR CONCENTRIC WITH SAID AXIS AND OF A RADIUS CONSIDERABLYSMALLER THAN THE RADIUS OF THE PARTICULAR COMPARTMENT, A SECOND SECTIONOF WHICH IS COMPOSED OF A FIRST SECTOR CONCENTRIC SAME RADIUS AS SAIDCOMPARTMENT, AND TWO CONVEX FURTHER SMOOTHLY CURVED SECTIONSINTERCONNECTING THE RESPECTIVE ENDS OF SAID FIRST AND SECOND SECTORS,SAID FURTHER SECTIONS HAVING END PORTIONS EXTENDING TANGENTIAL TORESPECTIVE ENDS OF SAID FIRST AND SECOND SECTORS, A SECOND ROTORJOURNALLED FOR ROTATION WITHIN THE OTHER ONE OF SAID COMPARTMENTS ABOUTTHE AXIS THEREOF AND HAVING A PERIPHERAL SURFACE OF CYLINDRICALFORMATION, THE CROSS SECTION OF WHICH IS THAT OF A DOUBLE BITTEDBATTLE-AXE AND COMPOSED OF A FIRST PAIR OF OPPOSITE SECTORS CONCENTRICWITH THE AXIS OF SAID OTHER COMPARTMENT AND OF SUBSTANTIALLY THE SAMERADIUS AS THIS COMPARTMENT, AND A SECOND PAIR OF OPPOSITE SECTORS OF AGENERALLY CONCAVE FORMATION INTERCONNECTING THE RESPECTIVE ENDS OF THESECTORS OF SAID FIRST PAIR OF OPPOSITE SECTORS, EACH SECTOR OF SAIDSECOND PAIR OF OPPOSED SECTORS HAVING A GENERALLY FLAT CENTRAL PORTIONAND ARCUATE END PORTIONS, THE SPACING OF SAID AXES BEING EQUAL TO THECOMBINED RADII OF SAID FIRST ROTOR FIRST SECTOR AND SAID SECOND ROTORFIRST SECTOR, A DRIVING CONNECTION BETWEEN SAID TWO ROTORS CAUSING SAIDSECOND ROTOR TO REVOLVE IN OPERATION IN THE OPPOSITE DIRECTION FROM THATOF SAID FIRST ROTOR AND WITH A ROTATIONAL SPEED EQUAL TO ONE HALF OF THEROTATIONAL SPEED OF SAID FIRST ROTOR, THE SHAPES OF SAID SECOND SECTORAND SAID FURTHER SECTIONS OF THE FIRST ROTOR AND SAID SECOND PAIR OFOPPOSITE SECTORS OF THE SECOND ROTOR BEING INTERRELATED IN SUCH A MANNERTHAT DURING OPERATION THE ROTORS CONTACT EACH OTHER AT LEAST ALONG ASINGLE LINE AT ALL TIMES, INLET AND OUTLET DUCTS IN SAID CASING LOCATEDONE ON EACH SIDE OF THE SECOND ROTOR AND COMMUNICATING WITH SAID WORKINGSPACE AND SEALED FROM EACH OTHER BY THE ROTORS, AND A CONTROL VALVEDISPOSED IN THAT ONE OF SAID DUCTS IN WHICH THE HIGHEST WORKING PRESSUREPREVAILS DURING OPERATION.